Photographic diffusion-transfer products comprising divalent metal-complexed antifoggant precursors and processes for their use

ABSTRACT

Metal-complexed antifoggant precursors of the formula A-X-A, wherein each A is an antifoggant nucleus resultant from the deprotonization of the antifoggant A-H, and X is a divalent metal, provide substantially no antifoggant functionality on photographic systems in which they are contained until cleavage of the antifoggant nuclei from the complex is accomplished.

United States Patent Carlson et al.

David P. Carlson, Westboro; Jerome L. Reid, Natick, both of Mass.

Polaroid Corporation, Cambridge, Mass.

Sept. 15, 1970 Related US. Application Data Continuation-impart of Ser. No. 756,884, Sept. 3, 1968, abandoned.

Inventors:

Assignee:

Filed:

Appl. No.:

[ Mar. 14, 1972 Primary Examiner-Norman G. Torchin Assistant ExaminerAlfonso T. Suro Pico Attorney-Brown and Mikula and Sheldon W. Rothstein [57] ABSTRACT Metal-complexed antifoggant precursors of the formula A- XA, wherein each A is an antifoggant nucleus resultant from the deprotonization of the antifoggant A--l-l, and X is a divalent metal, provide substantially no antifoggant functionality on photographic systems in which they are contained U.S. CL ..96/3, 96/56, 96/29 D until cleavage of the antifoggam nudei f the complex i me Cl ..G03c 5/54, G03e 1/34, G030 7/00 accomplished. Field of Search ..96/55, 3, 29 D, 56

31 Claims, 1 Drawing Figure IO F |2- VSUPPORT fie!) SENSITIVE SILVER HALIDE EMULSION LAYER -INTERLAYER GREEN SENSITIVE SID/ER HALIDE EMULSION LAYER VYELLOW DYE DEVELOPER LAYER AUXILIARY LAYER AQUEOUS ALKALINE PROCESSING COM POSITION IMAGE-RECEIVING LAYER P'SPACER LAYER N EUTRALIZING LAYER SUPPORT PATENTEDMAR 14 I972 3, 649, 267

l3 DYE DEVELOPER LAYER --7////////////7@msww ////////////7 DYE DEVELOPER LAYER SILVER HAUDE ///////////7 I9\E\\\\\\\\\\\\\\VYELLOW DYE DEVELOPER LAYER ////////////7 m m R uhik xxx kg mUm LAYER AQUEOUS ALKALINE PROCESSING OMPOSITION //////);/'VIMAGERECEIVING LAYER SUPPORT NTORS DA RLSDN JEROME L.RE|D lzow n w m ATTORNEYS PHOTOGRAPHIC DIFFUSION-TRANSFER PRODUCTS COMPRISING DIVALENT METAL-COMPLEXED ANTIFOGGANT PRECURSORS AND PROCESSES FOR THEIR USE This application is a continuation-in-part of copending application Ser. No. 756,884, filed on Sept. 3, 1968, in the names of David P. Carlson and Jerome L. Reid, now abandoned.

The present invention relates to photography and more particularly to photographic products and processes.

It has been extensively reported in literature pertaining to photography that photosensitive silver halide emulsions, and particularly photosensitive gelatino-silver halide emulsions, have a tendency to lose sensitivity and to become spontaneously developable without exposure to light. This phenomenon, characterized as chemical fog," may be defined as the density above base level that is developed in emulsion areas that have received no intentional exposure and, in general, is not uniformly distributed over a selectively photoexposed emulsion, being greatest in the unexposed areas and decreasing with increased exposure in a nonlinear manner.

In both silver and color photographic systems, the latter where silver halides are used to control image dye formation, fog results in a loss of image acuity.

Chemical fog may be divided into two classes: inherent fog, that is, fog which is emulsion initiated; and induced fog, that is, fog which is initiated during development. Induced fog appears to be due to physical development about extragranular centers and inherent fog is probably due to the presence of grains bearing a catalytic site sensitivity speck which is unavoidably introduced and which is equivalent in its properties to latent image. Induced fog accordingly may be unaffected by the level of inherent fog. Thus it will be readily appreciated that an emulsion susceptible to the development of chemical fog requires silver halide grains possessing a catalytic center of sufficient size to be spontaneously developable and/or grains unprotected from nondiscriminatory development.

Various and sundry procedures and additives have been disclosed in the art to provide an increase in the stability of photosensitive silver halide emulsions by reducing the tendency of photosensitive compositions to fog. These procedures usually increase the speed-to-fog ratio; otherwise there would be no point in using them unless the requirement for a low-fog level completely overrides that for sensitivity. In general, the methods available for the control of fog are to increase the bromide ion concentration during the emulsion fabrication process; select fog free gelatins, i.e., gelatins which are free of fogging contaminants and which have desirable ratios of restrainer to sensitizer; reduce the level of chemi cal sensitization; and add inorganic or organic fog-retarding adjuncts.

This invention relates primarily to the latter item above, and more particularly to the use of a specified class of organic antifoggant precursors.

Accordingly, it is a primary object of the present invention to provide novel photographic products, and processes utilizing same, which exhibit decreased susceptibility to fog formation.

Another object of the present invention is to provide novel processes and products, particularly adapted for obtaining monochromatic and multichromatic images by diffusion transfer, which exhibit decreased fog formation throughout an extended temperature range.

A still further object of the present invention is to provide novel photographic elements comprising not less than one silver halide emulsion having associated therewith specified transfer image-forming components which exhibit increased efiective processing temperature latitude.

Another object of the instant invention is to provide novel antifoggant precursors for use in photographic environments, said antifoggant precursors possessing substantially no antifoggant properties until contacted with a processing composition.

A further object of the instant invention is to provide a mechanism whereby the active site on a given antifoggant compound is masked until said compound is contacted with an alkaline-processing solution.

An additional object of the present invention is to provide novel hydrolyzable compounds which possess antifoggant properties only in their hydrolyzed state.

Another object of the present invention is to minimize changes in film speed of a given photographic system as a function of temperature and to control fog of said system throughout the operating temperature range thereof.

Other objects of the instant invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the process involving the several steps and the relation and order of one or more of such steps with respect to each of the others and the product possessing the features, properties and the relation of the elements which are exemplified in the following detailed disclosure and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention reference should be had to the following detailed description taken in connection with the accompanying drawing wherein:

The FIGURE is a diagrammatic enlarged cross-sectional view of one embodiment of a film unit for obtaining multicolor images by a diffusion transfer photographic process illustrating the association of elements during one stage of the performance of a diffusion transfer process, the thickness of the various materials being exaggerated.

In diffusion transfer processes for the formation of transfer images, an exposed photographic emulsion is developed and, substantially concurrently therewith, an imagewise distribution of transfer image-forming components is provided as a function of the point-to-point degree of development. At least part of that imagewise distribution is transferred by diffusion to a contiguous image-receiving layer to provide the desired transfer image formation to that layer.

In diffusion transfer processes for the formation of silver transfer images, an exposed silver halide emulsion is developed and, substantially concurrently therewith, an imagewise distribution of soluble silver complex is obtained by reaction of a silver solvent with silver halide of the emulsion as a function of its point-to-point degree of exposure. Preferably, the photosensitive silver halide emulsion is developed with a viscous processing composition which is spread between an element comprising the silver halide emulsion and a printreceiving element comprising a suitable silver precipitating layer. The processing composition affects development of the emulsion and substantially contemporaneously therewith forms a soluble silver complex, for example, a thiosulfate or thiocyanate, as a function of the point-to-point degree of emulsion exposure. This soluble silver complex is, at least in part, transported in the direction of the print-receiving element and the silver thereof is largely precipitated in the silver precipitating layer of said element to form a transfer image therein.

U.S. Pat. Nos. 2,647,049; 2,661,293; 2,698,798; and 2,802,735 disclose subtractive color diffusion transfer processes wherein color coupling techniques are utilized which comprise, at least in part, reacting one or more developing agents and one or more color formers, as a function of the photoexposure of a photographic emulsion, to provide a color image to a superposed image-receiving layer. U.S. Pat. No. 3.0l9,124 discloses the manufacture of photographic color screen elements particularly adapted for employment in multicolor diffusion transfer processes; and U.S. Pat. Nos. 2,968,554 and 2,983,606 disclose diffusion transfer processes wherein a color screen element is utilized to provide a multicolor transfer image to a superposed image-receiving layer. U.S. Pat. Nos. 2,774,668; 2,983,606; and 3,345,163 disclose diffusion transfer processes wherein complete dyes are utilized to provide a color transfer image to a superposed imagereceiving layer.

As disclosed in the aforementioned U.S. Pat. No. 2,983,606, a photosensitive element containing a dye developer and a silver halide emulsion is exposed and wetted by a liquid processing composition, for example, by emersion, coating, spraying, flowing, etc., in the dark, and the exposed photosensitive element is superposed prior to, during or after wetting on a sheetlike support element which may be utilized as an image-receiving element. In a preferred embodiment, the liquid-processing composition is applied to the photosensitive element in a substantially uniform layer as the photosensitive element is brought into superposed relationship with the image-receiving layer. The liquid-processing composition permeates the emulsion to initiate development. The dye developer is immobilized or precipitated in, for example, ex posed areas as a function of the development. Such immobilization is apparently, at least in part, due to a change in the solubility characteristics of the dye developer upon oxidation; particularly with regard to its solubility in alkaline solutions. It may also be due in part to a tanning effect on the emulsion by oxidized developing agent and in part to a localized exhaustion of alkali as a result of development. In the exposed and partially exposed areas of the emulsion, the dye developer, unreacted and dilfusible, provides an imagewise distribution of unoxidized dye developer dissolved in a liquidprocessing composition as a function of the point-to-point degree of exposure of the silver halide emulsion. At least part of this imagewise distribution of unoxidized dye developer is transferred by imbibition to a superposed image-receiving layer or element. Under certain conditions the layer of liquidprocessing composition may be utilized as the image-receiving layer. The image-receivin g element receives a depthwise diffusion of dye developer without appreciably disturbing the imagewise distribution thereof to provide the color transfer image. The image-receiving element may contain agents adapted to mordant or otherwise fix dye developer. If the color of the transferred dye developer is affected by change in the pH of the image-receiving element, this pH may be adjusted to provide a pH affording the desired color. The desired dye image carried by the image-receiving layer may be separated from the photosensitive element by stripping at the end of a suitable imbibition period.

Dye developers are compounds which contain in the same molecule both the chromophoric system of a dye and also a silver halide developing function. By a silver halide developing function is meant a grouping adapted to develop exposed silver halide. A preferred silver halide developing function is a hydroquinonyl group. Other suitable developing functions include ortho-dihydroxyphenyl and orthoand para-amino substituted hydroxyphenyl groups. In general, the development function includes a benzenoid developing function, that is, an aromatic developing group which forms quinonoid or quinone substances when oxidized.

An extensive compilation of such compounds is set forth in the aforementioned U.S. Pat. No. 2,983,606 and, in particular, in the various U.S. Patents and copending applications incorporated by reference therein.

In general, the preferred dye developers comprise monoazo and anthraquinone dyes which possess one or two hydroquinonyl groups attached to the auxochromophoric system of the dye by means of a conjugation-interrupting divalent group such as, for example, an alkylene group.

Multicolored images may be obtained using color imageforming components, such as, for example, the previously mentioned dye developers, in diffusion transfer processes, by several techniques. One such technique contemplates the use of a photosensitive silver halide stratum comprising at least two sets of selectively sensitized minute photosensitive elements arranged in the form of a photosensitive screen. Transfer processes of this type are disclosed in the previously noted U.S. Pat. No. 2,983,606. In such an embodiment each of the minute photosensitive elements has associated therewith an appropriate dye developer in or behind a silver halide emulsion portion. In general, a suitable photosensitive screen prepared in accordance with the disclosure of said patent comprises minute red sensitized emulsion elements, minute green sensitized emulsion elements and minute blue sensitized emulsion elements arranged in side-by-side relationship in a screen pattern and having associated therewith, respectively, a cyan dye developer, at magenta dye developer and a yellow dye developer.

Another process for obtaining multicolor transfer images utilizing dye developers employs an integral multilayer photosensitive element such as is disclosed in the aforementioned U.S. Pat. Nos. 2,983,606 and 3,345,163, wherein at least two selectively sensitized photosensitive strata and associated dye developers are superposed on a single support and are processed simultaneously and without separation with a single common image-receiving layer. A suitable arrangement of this type comprises a support carrying a red-sensitive silver halide emulsion stratum, a green-sensitive silver halide emulsion stratum, and a blue-sensitive silver halide emulsion stratum, said emulsions having associated therewith respectively, for example, cyan dye developer, a magenta dye developer and a yellow dye developer. The dye developer may be utilized in the silver halide emulsion layer, for example, in the form of particles, or it may be employed as a layer behind the appropriate silver halide emulsion stratum, for example, a layer of dye developer applied by the use of a coating solution containing about 0.5 to 8 percent, by weight, of the respective dye developer. Each set of silver halide emulsion and associated dye developer strata may be separated from other sets by suitable interlayers, for example, gelatin and the synthetic polymeric materials disclosed in U.S. Pat. No. 3,421,892. In certain instances it may be desirable to incorporate a yellow filter in front of the green-sensitive emulsion and such yellow filter may be incorporated in an interlayer. However, where desirable, a yellow dye developer of appropriate spectral characteristics which is present in a state capable of functioning as a yellow filter may be employed. In such instances a separate yellow filter may be omitted.

The preceding color image-forming components, that is, dye developers, are preferably selected for their ability to provide colors that are useful in carrying out subtractive color photography, i.e., cyan, magenta and yellow. It should be noted that it is within the scope of this invention to use mixtures of dye developers, for example, to obtain a desired color, e.g., black. Thus, it is to be understood that the expression color as used herein is intended to include the use of a plurality of colors to obtain black, as well as the use of a single black dye developer.

Copending U.S. application Ser. No. 234,864, filed Nov. 1, 1962, now U.S. Pat. No. 3,362,819, discloses image-receiving elements, particularly adapted foremployment in color diffusion transfer processes, for example, of the type disclosed in aforementioned U.S. Pat. No. 2,983,606, which comprise a support layer possessing on one surface thereof, in sequence, a polymeric acid layer, a timing layer or spacer layer in the preferred embodiment, and an image-receiving layer adapted to provide a visible image upon transfer to said layer of diffusible dye image-forming substance.

As set forth in the last-mentioned application, the polymeric acid layer comprises polymers which contain acid groups, such as carboxylic acid and sulfonic acid groups, which are capable of forming salts with alkali metals, such as sodium, potassium, etc., or with organic bases, particularly quaternary ammonium bases, such as tetramethyl ammonium hydroxide, or potentially acid-yielding groups, such as anhydrides or lactones, or other groups which are capable of reacting with bases to capture and retain them. The acid-reacting group is, of course, nondiffusible from the acid polymer layer. In the preferred embodiments disclosed, the acid polymer contains free carboxyl groups and the transfer-processing composition employed contains a large concentration of sodium and/or potassium ions. The acid polymers stated to be most useful are characterized by containing free carboxyl groups, being insoluble in water in the free acid form, and by forming watersoluble sodium and/or potassium salts. One may also employ polymers containing carboxylic acid anhydride groups, at least some of which preferably have been converted to free carboxyl groups prior to imbibition. While he most readily available polymeric acids are derivatives of cellulose or of vinyl polymers, polymeric acids from other classes of polymers may be used.

The acid polymer layer is disclosed to contain at least sufficient acid groups to effect a reduction in the pH of the image layer from a pH of about 12 to 14 to a pH of at least 11 or lower at the end of the imbibition period, and preferably to a pH of about 5 to 8 within a short time after imbibition. The pH of the processing composition employed preferably is of the order ofat least 12 to 14.

It is, of course, necessary that the action of the polymeric acid be so controlled as not to interfere with either development of the negative or image transfer of unoxidized dye developers. For this reason, the pH of the image layer is kept at a level of pH 12 to 14 until the positive dye image as been formed after which the pH is reduced very rapidly to at lest about pH 1 l, and preferably about pH 9 to 10, before the positive transfer image is separated and exposed to air. Unoxidized dye developers containing hydroquinonyl developing radicals diffuse from the negative to the positive as the sodium or other alkali salt. The diffusion rate of such dye image-forming components thus is at least partly a function of the alkali concentration, and it is desired that the pH of the image layer remain on the order of 12 to 14 until transfer of the necessary quantity of dye has been accomplished. The subsequent pH reduction, in addition to its desirable effect upon image light stability, serves a highly valuable photographic function by substantially terminating further dye transfer. The processing technique thus effectively minimizes changes in color balance as a result of longer imbibition times in multicolor transfer processes using multilayer negatives.

The spacer layer of the last-mentioned copending application, for example, an inert spacer layer comprising polyvinyl alcohol or gelatin or a temperature inversely permeable polymeric material as disclosed in U.S. Pat. No. 3,466,686 acts to time control the pH reduction by the polymeric acid layer. This timing is disclose to be a function of the rate at which the alkali diffuses through the spacer layer. It was stated to have been found that the pH does not drop until the alkali has passed through the spacer layer, i.e., the pH is not reduced to any significant extent by the mere diffusion into the interlayer but the pH drops quite rapidly once the alkali difiuses through the spacer layer.

As examples of materials, for use as the image-receiving layer, mention may be made of solution dyeable polymers such as nylon, as, for example, N-methoxymethyl polyhexamethylene adipamide; partially hydrolyzed polyvinyl acetate; polyvinyl alcohol with or without plasticizers; cellulose acetate with fillers, as, for example, one-half cellulose acetate and one-half oleic acid; gelatin; and other materials of a similar nature. Preferred materials comprise polyvinyl alcohol or gelatin containing a dye mordant such as poly-4-vinylpyridine, as disclosed in U.S. Pat. No. 3,148,061.

As has been alluded above, the presence of an antifoggant in a photographic system may be responsible for reducing both inherent and induced fog and will, therefore, produce a more attractive end product, both from aesthetic and technological points of view. Such products doubtless have a competitive advantage over other photographic products not quite as attractive or technologically efficient. The antifoggant composition is particularly helpful in minimizing or preventing reaction of a dye developer with unexposed silver halide and may be added to the processing composition and/or to one or more processing composition-permeable layers of the photosensitive and/or image-receiving elements. The pertinent art has recognized many compounds which have fog inhibiting characteristics, such as sodium and potassium bromide and iodide, certain imidazoles, triazoles, tetrazoles, thiazoles, indazoles, pyrazoles, pyrimidines, purenes, etc.

At low temperatures, when processing composition is distributed upon the contact surface of a selectively exposed photosensitive element of the aforementioned tripack configuration, development begins first in the blue-sensitive emulsion, since it contacts the processing composition before the 4 other layers. Temperature-retarded development, however, is slowed up even more by the restraining properties of antifoggant present and results, for example, in increased uncontrolled yellow dye developer transfer from the blue-sensitive emulsion to the image-receiving layer before complete developmental control has been established. This causes what may be termed yellow stain." It will be evident that at high temperatures the precise opposite happens, that is, the development rate is accelerated to a point where the restraining effect of the antifoggant is of insufficient consequence. The blue-sensitive emulsion will then be developed and the properly developed silver, combined with the fog present, will cause an overcontrol and thereby hold back the desired imagewise yellow dye diffusion and result in an undesired shift in color balance of the transfer image.

It has been discovered and claimed in copending application of Howard G. Rogers and Stanley M. Bloom filed on Sept. 3, 1968, Ser. No. 756,838, that a given antifogging composition may be modified in such a way as to mask the primary site or sites responsible for the antifogging effect, said masking moieties preventing interaction between photosensitive silver halides and the antifogging composition. As was pointed out therein, it has been found that if such moieties are capable of being removed from said compound by a mechanism such as, for example, hydrolysis, the antifogging nucleus will then be available to act upon the system. It will be evident that such a hydrolysis mechanism will be directly dependent upon the ambient temperature since the rate of hydrolysis is a direct function of temperature, said rate doubling approximately every 10 C. increase in temperature. Such hydrolyzable antifoggant precursors are preferably substantially nondiffusible and at least substantially less diffusible in their unhydrolyzed form than in their hydrolyzed form. It is theorized that the rate of hydrolysis of the said antifoggant precursors is dependent upon temperature, and, therefore, provides an effective means of controlling the availability of antifoggant in a given photographic system and insuring that development is carried out as unimpeded as possible by antifoggant effect in order to provide the optimum fog to image ratio which may be obtained at a given development temperature. It is also considered possible that, rather than the hydrolysis rate being the critical factor, the primary stimulus for the temperature-dependent release effect achieved herein may be solution rate; that is, the rate of solution of antifoggant precursor in processing composition may be the basic parameter in determining the amount of antifoggant available to the system at any given time. It is to be understood that the precise mechanism through which antifoggant is released into a photographic environment has not been definitely ascertained. Accordingly, the theories propounded herein are considered to be mere suggestions of possible mechanisms of operation and in no way limit the scope of the invention disclosed and claimed herein.

While antifoggant precursors which are readily hydrolyzable in acidic, basic and neutral mediums are contemplated by the instant invention it is preferred to utilize compounds which are principally base hydrolyzed or, more specifically, which are hydrolyzed to a greater degree in base than, for example, in water. The rate of release of such preferred compounds should be directly proportional to the concentration of hydroxyl ions, i.e., the higher the pH, the greater the rate of hydrolysis, temperature being constant. In instances where the antifoggant precursor is substantially hydrolyzed by water, said precursor may be encapsulated by any known technique in a medium which is saponified by, for example, alkaliprocessing composition as, for example, cellulose acetate, benzoic anhydride containing polymers, etc. and incorporated directly in the film unit to insure a long shelf life.

Generically speaking, the antifoggant precursors envisioned where X, Z and F are as described above. by the presentinvention are represented by the formula: As specific examples of heterocyclic ring systems contem- A-X-A plated for employment in the practice of the present invenwherein: A is an antifoggant nucleus derived from the tion, mention may be made of:

deprotonization of an active hydrogen site of the antifoggant A-H; and X is a divalent metal which, when complexed with the antifoggant nuclei A, produces a metal-antifoggant comr plex, the solubility and dissociation constant of which must be \I G SH less than that of the silver halide used in the photographic SH N H emulsion ofthe system being considered. 10 I i N it has been found that the requisite solubility and dissociation constant relativity exists when the divalent metal is selected from the group consisting of copper, zinc, mercury,

lead, tin, nickel, cadmium, cobalt, manganese, calcium and H iron. However, the denoted metals are not considered to be l; {l 1 115-0 c s 1 exclusive of other possible acceptable divalent metals, but are N H merely recitative of those metals which have demonstrated CH satisfactory complex formation within the context of the present invention. N S H In each instance of complex formation within the present invention, the divalent metal, X, links at least two molecules of 0 antifoggant through active hydrogen sites. It will, therefore, be ll appreciated that the antifoggant compositions utilized in the I 0-511 formation of the metal complex antifoggant precursors of the N present invention must contain at least one active hydrogen site which is available for complex formation by deprotonization. It will additionally be appreciated that the divalent metal selected must be photographically nondeleterious to the o-sH X k A /F Within the generic formula for the antifoggant precursors denoted above are two preferred classes of complexes which have been found to provide exceptionally good antifoggant functionality to a given system in the dissociated form, while providing a stable complex in the precursor form, said com- 5 plexes being substantially devoid of antifoggant functionality.

. H-C N The first preferred group within the generic expression may be g g visualized with reference to the formula:

process in which it is being utilized.

11. -N-XN- 40 and the like, in addition to those compounds identified specifically hereinafter. Preferred heterocyclic ring systems may, at the election of the operator, be substituted or unsubstituted.

In general, such substituents may be any of the various subwherein: X is a divalent metal selected from the group consiststituents which will enhance, or at least not deleteriously afing of op er, zin m r ur lead, tin, nickel, admiu fect, the antifoggant functionality of the selected heterocyclic cobalt, manganese, calcium, and iron; 2 is nitrogen or C-R ring configuration, which substituents are specifically conwhere R is hydrogen or lower alkyl; and F is the nonmetallic sidered to include annulated, aromatic and heterocyclic rings, atoms necessary to complete a heterocyclic antifoggant and substituents thereon, in addition to linear cyclic and l M arti la l within th in tant b la f th acyclic substituents of the aromatic, aliphatic, carbocyclic and generic expression defining the antifoggant precursors of the 5 heterocyclic series. It will be evident from the above discuspresem invcnfion are preferred if m represented b sion that the active hydrogen atom which is present on the anthe formula: tifoggant compositions which may be utilized in the present invention may be positioned either on a heterocyclic ring or III. N X N pendent therefrom as, for example, in a mercapto group.

/7\/ \/7\6 In certain instances, it is theorized that an oxy-complex will Z form with certain combinations of antifoggants and divalent Z k lair} metals; that is, there may be an oxy-link between the metal N N and a given molecule of antifoggant. Whether or not an oxylink occurs is immaterial to the practice of the instant invenwhere X and Z are as describd' f' g fi'y is nitrogerf tion since its presence or absence has no effect on the cleaved or carbon antzfoggant in a given photographic system, or on the cleavage The second preferred group within the generic expression mechanism which acts to free the amifoggam from may be visualized with reference to the formulas: divalent metal. Accordingly, the direct linkage notation, e.g., 7 V A-X-, is considered to be inclusive of possible complexes X which include the interposition of an oxygen atom between the metal and antifoggant nucleus constituents of a given antifogant precursor molecule within the context of the present n invention. 7 W Z It has been disclosed in US. Pat. No. 3,473,924 that certain compounds which may be generically defined as azabenzimidazoles provide excellent antifoggant functionality to photographic systems, and particularly diffusion transfer photographic systems, and may be adapted for advantageous employment therein to provide increased latitude at the temperature range which is considered operative for the given system. Such compounds have been found to inhibit the formation of fog with substantially no sacrifice in the effective speed of the photographic process in which it is utilized. In a particularly preferred embodiment, antifoggant precuri sors of the present invention may be derived from the azabenzimidazole nucleus and provide superior antifoggant t l activity to a given photographic system after hydrolysis of said I compounds has occurred. These compounds may generically s be represented by the formula: i l I VI. X

N/ N CSHgN N we c;

C I I N It poly(morcuric-mcrcaptobenzimidazolate) wherein: i CNZnN--C R is hydrogen or lower alkyl, i.e., containing less than six l; 1 l

carbon atoms; and X is as described above.

It will be appreciated particularly with reference to U.S. N N Pat. No. 3,473,924 cited above, that the compounds Zinc bismhenyltetmzolat" represented by formulas Ill and V, above, may contain various N Cu N substituents in the 5 and/or 6 position which enhance the an- 0 tifoggant functionality of the compounds and are considered 2 CH HO I 2 to be included within the scope of the present invention. More particularly, among the substituents which may be substituted N in the 5 and/or 6 position are halogen, lower alkyl, e.g., con- C0 per bis- -nitrobonzimidazolate tammg less than six carbon atoms, mtro, amino, hydroxy, p p

lower alkoxy, i.e., containing less than six carbon atoms, aryl, sulfonamido, and carboxamido groups, it being understood NCS-Pb-S-CN that such substituents may together constitute the atoms l l H l necessary to complete a cyclic structure, as, for example, N/ N/ N 7 Lead bis-l-phenylfi'i-morcaptotetrazolate R I- N N N% Sn-S$|J CSSHSC C-S- 11-0 ll nil l H 40 y F i It has been theorized that the antifoggant compounds dis- H: playing the strongest antifoggant activity possess weak elecpolylstannus-(A-methyl-Q:6-mercaptopyrimidinate)] tron donor moieties at the 5 and/or 6 position in the generic formula next above. Accordingly, in the most preferred embodiments of the present invention substituents in the 5 and/or N N 6 position should inherently be weak electron donors. It will be additionally appreciated that R and any substituents which C may be in the 5 and/or 6 position above are intended to encompass equivalents thereof including situations wherein the H H substituents in the 5 and 6 position, above, are taken together nickel bls'indazolate to form an annulated hydrocarbon ring system.

In instances where, for example, complexes of lead, tin, zinc HCCSFe /N\ and copper are formed from ammoniacal solution, the molar i HO N ratio of antifoggant to metal may be greater than two to one. N Under these conditions, two extra moles of antifoggant may N H S-Fe-N associate with the metal through coordinate covalent bonds Ho resulting in a four to one molar ratio of antifoggant moieties to 1 divalent metal. li L l In the event that the antifoggant nucleus contains more than one active hydrogen position it will be appreciated that the poly (ferrous mercaptopymzome) divalent metal utilized may attach in more than one position N-ZnN and will, therefore, form polymeric antifoggant metal com- Br Br plexes. Such materials will hydrolyze according to the same I OH HC mechanism which hydrolyzes the bis-organic complex form (3113 CH3 and are specifically included in t lie coritextof th e pi'esentin N N N N vention. zinc-bis-(5-methyl-6-bromo-4-azabeuzimidazolate) Exemplary antifoggant precursors within the context of the I present invention are: NCd-N calcium bis-selenol imidazole cadmium-bis-benzotriazolate mnnganese-bis-(fi-methylb-bmmot azabenzimidazolate) Zu {l N/Zn N Zn N/ J N K N LN \N/ poly(zinc-fi-mereapto-purinate) The formation of the metal antifoggant complexes of the present invention may be appreciated with reference to the following equations:

2A-H X Q&AXA 2H wherein: A and X are as described above, and Q is an anion. For example, the formation of a zinc benzotriazole complex utilizing zinc nitrate would occur according to the following reaction:

Mercapto-substituted antifoggants, for example, the mercaptotetrazoles undergo similar reactions in which the hydrogen of the mercapto group reacts to give a metal mercaptotetrazole complex. Reactions of this type were investigated by Remington and Meyer, Diss. Abstracts No. 24, Columbus, Ohio, Ohio State Press, 1937; and Curtis, Industrial and Chemical Analytical, Edition 13, 349-351 (1941).

Under conditions of normal storage the dissociation constant of the metal-antifoggant complex is sufficiently low as to make the free antifoggant available to the silver halide insufficient to cause desensitization. Under the conditions of processing, either by an increase of pH, and/or in conjunction with the use of a chelating agent whose metal chelate complex has a lower dissociation constant than the metal-antifoggant chelate, a change in the dissociation constant for the metal-antifoggant chelate has been found to stimulate an increase in the concentration of free antifoggant during a desired period.

Alkaline-processing compositions supply hydroxyl ions which, in most instances, provide chelation with the metal of the antifoggant complex to stimulate cleavage of antifoggant ions from said complex thereby providing antifoggant functionality to a given photographic system. Where hydroxyl ions do not provide the requisite stimulus in a desired time interval, dissociation accelerators as, for example, ethylene diamine tetraacetic acid; triethanolamine, a-hydroxy acid salts, such As is discussed in Example 2, below, zinc-bis-benzotriazolate, .when used alone, provides poor antifoggant activity to a' photographic system in which development is completed in a short time, e.g., under approximately 60 seconds, due to slow degradation. In such instances, the addition of a dissociationaccelerating compound which will provide chelation with the complexed metal accelerates precursor dissociation and extends the usefulness of such precursors to systems such as those of the instant invention.

As has been stated above, the activity of the antifoggants which may be utilized in the context of the present invention is due to the presence of one or more acidic hydrogens which are replaceable by silver. Where the hydrogen is replaced by a metal cation to form an insoluble complex, the antifoggant properties for a given quantity of antifoggant compound are extinguished. Due to the fact that zinc is less likely to introduce undesirable photographic side effects into a given photographic system than other divalent metals, its use is encouraged in preferred embodiments. Utilizing the antifoggant system of the present invention, it will be appreciated that regeneration of the antifoggant, for example, zinc -bis-phenyl mercaptotetrazolate is governed, to a certain degree, by diffusion of hydroxyl ions at a given temperature, but to a more marked degree by the subsequent temperature-dependent kinetics of the reaction, for exam ple:

The zinc bis-phenyl mercaptotetrazolate is insoluble while the phenyl mercaptotetrazole alkali salt and zinc hydroxide are soluble in the environment of the developing photographic systems. The free antifoggant can therefore be made available to the silver after initiation of development by positioning the metal salt in a spacer layer, dye layer, or even in the silver layer under certain conditions without causing desensitization under normal storage,

At the option of the operator it has been determined that the antifoggant precursors of the present invention may be used alone or in conjunction with viable antifoggants. For example, with respect to a typical color film processing composition containing a conventional antifoggant, such as benzotriazole and the like, generally in the order of about 2 percent, the antifoggants of the present invention may be added to the system with a concomitant reduction in the percentage of or elimination of the benzotriazole or like antifoggant. Under certain conditions utilization of small amounts of a second antifoggant may be found desirable to provide limited antifogging and restraining properties at very low temperatures.

In a preferred embodiment of the pre sent invention, 5 photosensitive element is employed which is specifically adapted to provide for the production of a multicolor dye transfer image and comprises a dimensionally stable support layer carrying at least two selectively sensitized silver halide emulsion strata each having a dye developer material of predetermined color associated therewith which is soluble and diffusible in alkali at a first pH.

The preferred photosensitive image-receiving element comprises an alkaline solution permeable polymeric layer dyeable by the dye developer; a polymeric spacer layer comprising a polymer possessing decreasing alkaline solution permeability ,with increasing temperature; an alkaline solution permeable polymeric acid layer containing sufficient acidifying groups to effect reduction, subsequent to substantial multicolor transfer dye image formation, of the image-receiving element from the first pH to a second pH, at which the dye image-providing material is insoluble and nondiffusible; and a dimensionally stable support layer.

The silver halide emulsions comprising the multicolor photosensitive laminate preferably possess predominant spectral sensitivity to separate regions of the spectrum and each has associated therewith a dye, which is a silver halide developing agent and is, most preferably, substantially soluble in the reduced form only at the first pI-l, possessing a spectral absorption range substantially complementary to the predominant sensitivity range of its associated emulsion. In the preferred embodiment, each of the emulsion strata, and its associated dye, is separated from the remaining emulsion strata, and their associated dye, by separate alkaline solution permeable polymeric interlayers.

In such preferred embodiment of the invention, the silver halide emulsion comprises photosensitive silver halide dispersed in gelatin and is about 0.6 to 6 microns in thickness; the dye itself is dispersed in an aqueous alkaline solution polymeric binder, preferably gelatin, as a separate layer about 1 to 7 microns in thickness; the alkaline solution permeable polymeric interlayers, preferably gelatin, are about 1 to 5 microns in thickness; the alkaline solution permeable and dyeable polymeric layer is transparent and about 0.25 to 0.4 mil. in thickness; the polymeric spacer layer intermediate the dyeable polymeric layer and the polymeric acid layer is transparent and about 0.1 to 0.7 mil. in thickness; the alkaline solution permeable polymeric acid layer is transparent and about 0.3 to 1.5 mils. in thickness; and each ofthe dimensionally stable support layers are alkaline solution impermeable and about 2 to 6 mils. in thickness. It will be specifically recognized that the relative dimensions recited above may be appropriately modified, in accordance with the desires of the operator, with respect to the specific product to be ultimately prepared.

In the preferred embodiment of the present inventions film unit for the production of a multicolor transfer image, the respective silver halide/dye developer units of the photosensitive element will be in the form of a tripack configuration which will ordinarily comprise a cyan dye developer/red-sensitive emulsion unit contiguous the dimensionally stable support layer, the yellow dye developer/blue-sensitive emulsion unit most distant from the support layer and the magenta dye developer/green-sensitive emulsion unit intermediate those units, recognizing that the relative order of such units may be varied in accordance with the desires of the operator.

Reference is now made to FIG. 1 of the drawings wherein As illustrated in FIG. 1, film unit 10 comprises a photosensitive laminate 11 including, in order, dimensionally stable support layer 12, preferably a flexible sheet material; cyan dye developer layer 13; red-sensitive silver halide emulsion layer 14; interlayer 15, magenta dye developer layer 16; green-sensitive silver halide emulsion layer 17; interlayer 18; yellow dye developer layer 19; blue-sensitive silver halide emulsion layer 20; auxiliary layer 21, which may contain an auxiliary silver halide developing agent; and an image-receiving element 22,v including image-receiving layer 23; spacer layer 24; neutralizing layer 25; and dimensionally stable support layer 26, preferably a flexible sheet material.

As shown in the drawing, the multilayer exposed photosensitive element 11 is shown in processing relationship with an image-receiving element 22 and a layer 27 of processing solution distributed intermediate elements 11 and 22,

In the performance of a diffusion transfer multicolor process employing film unit 10, the unit is exposed to radiation, actinic to photosensitive laminate 11.

Subsequent to exposure, film unit 10 may be processed by being passed through opposed suitably gapped rolls in order to apply compressive pressure to a frangible container in order and to effect rupture of the container and distribution of alkaline processing composition 27, having a pH at which the cyan, magenta and yellow dye developers are soluble and diffusible, intermediate dyeable polymeric layer 23 and auxiliary layer 21.

Alkaline-processing solution 27 permeates emulsion layers l4, l7 and 20 to initiate development of the latent images contained in the respective emulsions. The cyan, magenta and yellow dye developers, of layers 14, 17 and 20, are immobilized, as a function of the development of their respective associated silver halide emulsions, preferably substantially as a result of their conversion from the reduced form to their relatively insoluble and nondiffusible oxidized form, thereby providing imagewise distributions of mobile, soluble and diffusible cyan, magenta and yellow dye developer, as a function of the pointto-point degree of their associated emulsions exposure. At least part of the imagewise distributions of mobile cyan, magenta and yellow dye developer transfers, by diffusion, to aqueous alkaline solution permeable polymeric layer 23 to provide a multicolor dye transfer image to that layer. Subsequent to substantial transfer image formation, a sufficient portion of the ions comprising aqueous alkaline solution 27 transfers, by diffusion, through permeable polymeric layer 23, permeable spacer layer 24, and to permeable polymeric acid layer 25, whereby alkaline solution 27 decreases in pH, as a function of neutralization, to a pH at which the cyan, magenta and yellow dye developers, in the reduced form, are insoluble and nondiffusible, to provide thereby a stable multicolor dye transfer image.

Subsequent to substantial transfer image formation, printreceiving element 22 may be manually dissociated from the remainder of the film unit, for example, by stripping.

The following examples are considered illustrative only and should not be taken in a limiting sense.

EXAMPLE 1 The compound, zinc bis-benzotriazolate,

is synthesized according to the following procedure:

1 mole of benzotriazole is dissolved in 500 ml. of water containing 75 cc. of concentrated ammonia. 0.48 mole of Zn(NO l-l O is dissolved in 500 ml. of water containing an additional l50 cc. of concentrated ammonia. It is added to the benzotriazole solution with rapid stirring and continuous agitation for 15 minutes. A white precipitate was allowed to sit for an additional l5 minutes before the pH was adjusted to 5.8 with acetic acid. The precipitate was washed with distilled water several times and finally with 500 ml. of 1:1 wateracetone mixture. The above synthesis provided dibenzotriazole zincate of individual particle size less than 3 microns, but on dispersion in gelatin, the suspension consisted of aggregates 5 to 10 microns in diameter.

Subsequent preparation of zinc bis-benzotriazolate according to the above procedure, precipitated in the presence of gelatin followed by setting, noodling and washing of noodles gave a well-dispersed suspension of individual particles less than 3 microns in diameter.

While the instant compound has been empirically denoted as comprising a two to one molar ratio of benzotriazole to antifoggant, it will be appreciated in view of the discussion hereinbefore that the precise molar ratio in some of the prepared compound may be four to one since it was precipitated from ammoniacal solution.

EXAMPLE 2 An image-receiving sheet was prepared by coating a cellulose nitrate subcoated baryta paper with the partial butyl esterof polyethylene/maleic anhydride copolymer prepared by refluxing, for 14 hours, 300 gms. of DX-840-31 Resin [trade name of Monsanto Chemical Co., St. Louis, Missouri, for high-viscosity poly-(ethylene/maleic anhydridefl, 140 gms. of n-butyl alcohol and 1 cc. of 85 percent phosphoric acid to provide a polymeric acid layer approximately 0.3 mils. thick. The external surface of the acid layer was coated with a 4 percent solution of polyvinyl alcohol in water-methanol-iso-propanol to provide a polymeric spacer layer approximately 0.15 mils thick. The external surface of the spacer layer was then coated with a 2:1 mixture, by weight, of polyvinyl alcohol and poly-4- vinylpyridine, at a coverage of approximately 600 mgs. per square foot, to provide a polymeric image-receiving layer approximately 0.40 mils thick. The thus-prepared image-receiving element was then baked at 180 F. for 30 minutes and then allowed to cool.

In order to provide comparative data on the utilization of the antifoggant compounds of the present invention a control photosensitive element, Element 1, was formulated by first coating a support member with 100 mg. per square foot of cyan dye developer, overcoating that layer with 300 mg. per square foot of red-sensitized silver halide emulsion, and finally overcoating the silver halide emulsion layer with 30 gms. per square foot of methylphenyl hydroquinone dispersed in 30 mg. per square foot of gelatin. Two additional sheets were made according to the following constituency.

Element 2 is identical to Element 1, except that 30 mg. of phenylmercaptotetrazole as zinc bis-phenylmercapto-tetrazolate was dispersed in the silver halide layer.

Element 3 is identical to Element 1, except that 60 mgs. of phenylmercaptotetrazole as zinc bis-phenylmercaptotetra-zolate were dispersed in the methylphenyl hydroquinone-gelatin layer.

All of the cyan monochrome negative elements were exposed to a step wedge to selectively filtered radiation and processed by spreading an aqueous liquid-processing composition between said cyan monochrome and the abovedescribed image-receiving sheet as they were bought into superposed relationship in the absence of actinic radiation. After an imbibition period of 60 seconds, the image-receiving sheet was separated from the remainder of the film assembly. The processing composition utilized for the instant experiment comprised the following ingredients:

Water 100 cc. Hydroxyethyl cellulose 3.8 gs. Potassium Hydroxide l 1.2 gs. BenZyLa-picolinium bromide gs.

A second processing composition used for comparative testing was formulated according to the above-denoted constituents and amounts and additionally included 3.5 gins. of 'benzotriazole.

Measurements were made of the relative speed of the photosensitive elements and of the differential dye densities obtained (AD). For purposes of the instant experiment, differential dye density is considered to be D minus D where D,,,, represents the density of the saturated monochrome and D,,,,,, represents the stain present.

The following tabulations collectively and succinctly present the results achieved during the instant comparative testing:

TABLE I Effect of Antifoggants on Cyan Monochrome Sensitivity v Processing Composition w/benzotriazole wlo benzotriazole Element No. 1 No. l No. 2 No. 3

AD 098 0.25 1.5! L5] TABLE IL-EFFECT OF AN'IIFOGGAN'I 1N NEGATIVE ON TEMPERATURE PERFORMANCE Processing composition w/benzotriazole w/o benzotriazole Element No. 1 Element No. 3

Processed at- 45 F. 75 F. F. 45 F. 75 F. 95 F.

AD 1.08 0.98 0.94 1.23 1.54 1.11 Relative speed 2.07 2. 47 2. 65 2. 24 2.54 2. 51

Next, the effect of zinc bis-phenylmercaptotetra-zolate on sensitometry after an accelerated storage period was performed by placing sample ingredients utilized in the experiment in a F 45 percent relative humidity incubation condition for 7 days. The following comparative data demonstrates the results attained:

TABLE Il'1'.-EFFECT OF ANTIFOGGANT 1N NEGATIVE ON %IIE(NBSIITOMETRY AFTER 7-DAY, 120 F., 45% R.H. INCUBA- Processing composition w/benzotriazole w/o benzotriazole Element N o. 1 Element No. 3

After After Processed at R.I Initial 7 days Initial 7 days AD 0.98 0.39 1.51 1. 52 Relative speed 2. 4 2. 54 2. 35

Coating No. 3 processed with a reagent containing no antifoggant performed better than coating No. l utilizing the standard antifoggant, benzotriazole, and was markedly better on accelerated storage testing. In addition, the silver development induction period is shorter, the development rate is faster, and fog is lower.

In the instance where the effect of monochrome sensitivity of elements 2 and 3 are compared with element 1, processed with and without benzotriazole antifoggant, it is quite clearthat markedly better results are achieved with antifoggant complexes of the present invention. This same result is additionally evident at the various temperatures at which processing is carried out in Tables 11 and 111 and, from Table 11, it will be appreciated that the compounds of the present invention produce a marked increase in red speed.

Similar experiments were run with zinc bis-benzotriazolate and very little antifogging activity was attributed thereto during the processing period.

7 The difieriic' in betra of ii zirEbhb ehiotria zolat and zinc bis-phenylmercaptotetrazolate is not unexpected. Equimolar quantities of the two salts treated with an excess of potassium hydroxide at room temperature show that the zinc bis-phenylmercaptotetrazolate completely dissolved or was completely hydrolyzed in less than 5 seconds, whereas the zinc bis-benzotriazolate took approximately 30 seconds for hydrolysis. Accordingly, it will be seen that in view of the discussion hereinbefore concerning metal chelating accelerators, the

utilization of such compounds with zinc bis-benzotriazolate would obviously provide a usable system, even for a photographic process which is carried out during, for example, a 60- second interval.

It will be appreciated that the 60 mg. per square foot coverage of phenylmercaptotetrazole as the zinc salt does not cause a loss of speed at room temperature. In general, the optimum concentration of the agent to be employed as an an- :tifoggant precursor should be determined empirically for each given specific photographic system. A typical concentration range is between 0.005 to 5.0 mgs. of free antifoggant per mg. of silver halide present in the silver halide emulsion of concern depending on the fogging characteristics of said emulsion. Although concentrations in excess of the given range may be employed an increase in the concentration beyond certain empirical limits generally provides no additional beneficial results. Conversely, concentrations below that of the designated range merely decrease fog control at high temperatures below the effective levels generally sought but, nonetheless, do not negate the achievement of some beneficial fog control.

The agents themselves may be initially disposed in any one or more processing composition permeable layers of the film units photosensitive and/or image-receiving elements, at any stage during their manufacture. In addition, the bulkiness of specific antifoggant nucleus materials may be adjusted to provide an anchoring or diffusion-inhibiting function within a given photographic system. Such a design might easily be applicable to situations where it is desirable to lodalize antifoggant activity in the immediate vicinity of a given emulsion in order to maintain a desired antifoggant concentration range in the area of that emulsion. Moieties which have been found quite useful for this purpose are long chain fatty acid groups as, for example, octyl, stearyl, etc.

It should also be appreciated that the time within the development cycle at which the antifoggant composition sees the alkaline-processing composition may be adjusted by judicious placement of said antifoggant within the photographic system. In this manner it will be seen that the release of antifoggant for use in conjunction with a given emulsion may be delayed until the end of the fog induction period in the antifoggant-associated emulsion.

The liquid-processing composition referred to for effecting monochromatic and multicolor transfer processes comprises at least an aqueous solution of an alkaline compound, for example, diethylamine, sodium hydroxide sodium carbonate, etc. and possesses a pH in excess of 12 preferably. If the liquid processing composition is to be applied to the emulsion by being spread thereon, preferably in a relatively thin uniform layer, it may include a viscosity increasing compound constituting a film-forming material of the type which, when said composition is spread and dried, forms a relatively firm and relatively stable film. A preferred film-forming material is a high molecular weight polymer such as a polymeric, watersoluble ether which is inert to an alkaline solution such as, for example, a hydroxyethyl cellulose or sodium carboxymethyl cellulose. Other film-forming materials or thickening agents whose ability to increase viscosity is substantially unaffected if left in solution for a long period of time may also be used. The film-forming material is preferably contained in the processing composition in suitable quantities to impart to said composition a viscosity in excess of 1,000 centipoises at a temperature of approximately 24 C. and preferably of the order of 1,000 to 200,000 centipoises at said temperature. Illustrations of suitable liquid-processing compositions may be found in the several patents and copending applications herein mentioned and also in examples herein given. Under certain circumstances, it may be desirable to apply a liquid processing composition to the photosensitive element prior to exposure, in accordance with the technique described in U.S. Pat. No. 3,087,816, issued Apr. 30, 1963.

It will be noted that the liquid-processing composition employed may contain an auxiliary or accelerating developing agent, such as p-methylaminophenol, 2,4-diamino-phenol, pbenzylaminophenol, hydroquinone, toluhydroquinone, phenylhydroquinone, 4'-methylphenylhydroquinone, etc. It is also contemplated to employ a plurality of auxiliary or accelerating developing agents, such as a 3-pyrazolidone developing agent and a benzenoid developing agent, as disclosed in U.S. Pat. No. 3,039,869, issued June 19, 1962. As examples of suitable combinations of auxiliary developing agents, mention may be made of l-phenyl-3-pyrazolidone in combination with pbenzylaminophenol and l-phenyl-3-pyrazolidone in combination with 2,5-bis-ethyleneimino-hydroquinone. Such auxiliary developing agents may be employed in the liquid processing composition or they may be initially incorporated, at least in part, in one or more permeable strata of the film unit. It may be noted that at least a portion of the dye developer oxidized during development may be oxidized and immobilized as a result of a reaction, e.g., an energy-transfer reaction, with the oxidation product of an oxidized auxiliary developing agent, the latter developing agent being oxidized by the development of exposed silver halide. Such a reaction of oxidized developing agent with unoxidized dye developer would regenerate the auxiliary developing agent for further reaction with the exposed silver halide.

In addition, development may be desirably effected in the presence of an onium compound, particularly a quaternary ammonium compound, in accordance with the processes disclosed in U.S. Pat. No. l %,l 73,786.

The support layers referred to may comprise any of the various types of conventional rigid or flexible supports, for example, glass, paper, metal, and polymeric films of both synthetic types and those derived from naturally occurring products. Suitable materials include paper; aluminum; polymethacrylic acid, methyl and ethylesters; vinyl chloride polymers; polyvinyl acetal; polyamides such as nylon; polyesters such as polymeric films derived from ethylene glycol terephthalic acid and cellulose derivatives such as cellulose acetate, triacetate, nitrate, propionate, butyrate, acetate-propionate, or acetatebutyrate.

It will be understood that silver halides of varying halide concentrations may be advantageously employed and that the silver halide emulsions employed may be sensitized chemically and optically by any of the accepted procedures.

While a rupturable container provides a convenient means for spreading a liquid processing composition between layers of a film unit whereby to permit the processing to be carried out with a camera apparatus, the practices of this invention may be otherwise effected. For example, a photosensitive element, after exposure in suitable apparatus and while preventing further exposure thereafter to actinic light, may be removed from such apparatus and permeated with the liquidprocessing composition, as by coating the composition on said photosensitive element or otherwise wetting said element with the composition, following which the permeated, exposed photosensitive element, still without additional exposure to actinic light, is brought into contact with the image-receiving element for image formation in the manner heretofore described.

In examples of this specification, percentages of components are given by weight unless otherwise indicated.

Throughout the specification and claims, the expression superposing has been used. This expression is intended to cover the arrangement of two layers in overlying relation to each other either in face-to-face contact or in separated condition and including between them at least one layer or stratum of a material which may be a viscous liquid. Further more, the term lower alkyl, unless otherwise denoted, indicates an alkyl group containing less than six carbon atoms.

Since certain changes may be made in the above products, compositions and processes without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

We claim:

1. In a process for forming a photographic image which comprises the step of developing an exposed photosensitive element containing a silver halide emulsion with an aqueous processing composition, the improvement which comprises conducting said process in the presence of a processing composition hydrolyzable antifoggant precursor represented by the formula:

A-X-A where each A is an antifoggant nucleus selected from the group consisting of Z is selected from the group consisting of nitrogen or CR where R is selected from the group consisting of hydrogen or lower alkyl; F is the nonmetallic atoms necessary to complete a heterocyclic antifoggant nucleus; and X is a divalent metal selected from the group consisting of copper, zinc, mercury, lead, tin, nickel, cadmium, cobalt, manganese, calcium, or iron wherein said metal is joined to each antifoggant nucleus through a position on each nucleus which imparts antifoggant functionality thereto, thereby rendering said antifoggant nucleus impotent as an antifoggant during the period of attachment to said divalent metal.

2. The process of claim 1 wherein said antifoggant precursor is represented by the formula:

wherein X is a divalent metal selected from the group consisting of copper, zinc, mercury, lead, tin, nickel, cadmium, cobalt, manganese, calcium and iron; Z is selected from the group consisting of nitrogen or C-R wherein R is selected from the group consisting of hydrogen or lower alkyl; and F is the nonmetallic atoms necessary to complete a heterocyclic antifoggant nucleus.

3. The process of claim 1 wherein said antifoggant precursor is represented by the formula:

wherein X is a divalent metal selected from the group consisting of copper, zinc, mercury, lead, tin, nickel, cadmium, cobalt, manganese, calcium and iron; Z is selected from the group consisting of nitrogen or C-R where R is selected from the group consisting of hydrogen or lower alkyl; and F is the nonmetallic atoms necessary to complete a heterocyclic antifoggant nucleus.

5. The process of claim 2 wherein said antifoggant precursor is represented by the formula:

where X is a divalent metal selected from the group consisting of copper, zinc, mercury, lead, tin, nickel, cadmium, cobalt, manganese, calcium or iron; and R is selected from the group consisting of hydrogen and lower alkyl.

7. The process of claimfi wherein said compound is zinc bis- S:rneth yl-6-brorno-4-azabe nzimidazolate].

8. The process of claim 5 which includes the steps of developing said exposed photosensitive element with an aqueous alkaline processing composition forming thereby an imagewise distribution of image-forming components in said photosensitive element as a function of the point-to-point degree of exposure thereof and transferring at least part of said imagewise distribution by diffusion to a contiguous image-receiving layer to provide thereto a photographic diffusion transfer image.

9. The process of claim 8 wherein said image-forming components comprise a soluble silver complex.

10. The process of claim 8 wherein said image-forming components comprise color image-forming materials.

11. The process of claim 10 wherein said color image-forming components comprise at least one dye which is a silver halide developing agent.

12. The process of claim 11 which includes, in combination,

the steps of exposing a photosensitive element which comprises at least two selectively sensitized silver halide emulsion layers each having a dye of predetermined color associated therewith, which dye is a silver halide developing agent and is processing composition soluble and diffusible in alkali, contacting said exposed photosensitive element with an aqueous alkaline-processing composition and effecting thereby hydrolytic removal of said antifoggant moieties from said divalent metal as a function of processing temperature and development of the latent images contained in each of said silver halide emulsions, immobilizing the dye associated with each of said emulsions as a result of said development and forming thereby an imagewise distribution of mobile dye as a function of the point-to-point degree inbibition, exposure thereof. and transferring, by imbibition at least a portion of each of said imagewise distributions of mobile dye to a superposed image-receiving element to provide thereto a multicolor dye transfer image. I

13. The process of claim 12 which includes, in combination, the steps of exposing a photosensitive element comprising blue-sensitive, green-sensitive and red-sensitive silver halide emulsion layers mounted on a common support, each of said blue-sensitive, green-sensitive and red-sensitive silver halide emulsion layers having associated therewith, respectively, yellow, magenta and cyan dyes, each of said dyes being a silver halide developing agent soluble and diffusible in alkali; contacting said exposed photosensitive element with an aqueous alkaline processing composition effecting thereby hydrolytic removal of said antifoggant moieties from said divalent metal as a function of processing temperature and development of the latent image contained in each silver halide emulsion; immobilizing said yellow, magenta and cyan dye as a function of development of their respective associated silver halide emulsions forming thereby imagewise distributions of mobile yellow, magenta and cyan dye; and transferring, by imbibition, at least a portion of each of said imagewise distributions of mobile yellow, magenta and cyan dye to a superposed imagereceiving element to provide thereto a multicolor dye transfer image.

14. The process of claim 13 wherein said antifoggant precursor is zinc bis-[-methyl-6-bromo-4-azabenzi-midazolate].

15. As a product, a photosensitive element which comprises a support layer carrying a photosensitive silver halide emulsion having associated therewith a hydrolyzable antifoggant precursor represented by the formula:

A-X-A where each A is an antifoggant nucleus selected from the group consisting of Z is selected from the group consisting of nitrogen or C-R where R is selected from the group consisting of hydrogen or lower alkyl; F is the nonmetallic atoms necessary to complete a heterocyclic antifoggant nucleus; and X is a divalent metal selected from the group consisting of copper, zinc, mercury, lead, tin, nickel, cadmium, cobalt, manganese, calcium, or iron wherein said metal is joined to each antifoggant nucleus through a position on each nucleus which imparts antifoggant; functionality thereto, thereby rendering said antifoggant nucleus impotent as an antifoggant during the period of attachment to said divalent metal.

16. The product of claim 15 wherein said antifoggant precursor is represented by the formula:

.wherein X is a divalent metal selected from the group consisting of copper, zinc, mercury, lead, tin, nickel, cadmium, cobalt, manganese, calcium and iron; 2 is selected from the group consisting of nitrogen or C-R where R is selected from the group consisting of hydrogen or lower alkyl; and F is the nonmetallic atoms necessary to complete a heterocyclic antifoggant nucleus.

18. The product of claim 15 wherein said antifoggant precursor is represented by the formula:

wherein X is a divalent metal selected from the group consisting of copper, zinc, mercury, lead, tin, nickel, cadmium, cobalt, manganese, calcium and iron; 2 is selected from the group consisting of nitrogen or C-R where R is selected from the group consisting of hydrogen or lower alkyl; and F is the nonmetallic atoms necessary to complete a heterocyclic antifoggant nucleus.

19. The product of claim 15 wherein said antifoggant precursor is represented by the formula:

wherein X is a divalent metal selected from the group consisting of copper, zinc, mercury, lead, tin, nickel, cadmium, cobalt, manganese, calcium and iron; Y is carbon or nitrogen; and Z is selected from the group consisting of nitrogen or C-R where R is selected from the group consisting of hydrogen or lower alkyl.

20. The product of claim 19 wherein said antifoggant precursor is represented by the formula:

(T 1? n Nl AN/ wherein X is a divalent metal selected from the group consisting of copper, zinc, mercury, lead, tin, nickel, cadmium, cobalt, manganese, calcium and iron; and R is selected from the group consisting of hydrogen and lower alkyl.

21. The product of claim 20 wherein said antifoggant precursor is zinc bis-[5-methyl-6-bromo-4-azabenzimidazolate].

22. The product of claim 15 wherein said silver halide emulsion has associated therewith a dye which is a silver halide developing agent.

23. The product of claim 22 wherein said dye is dispersed in a separate layer intermediate said silver halide emulsion and said support,

24. The product of claim 15 wherein said support carries on one surface at least two selectively sensitized silver halide emulsion layers, each having associated therewith a dye which is a silver halide developing agent of a predetermined color.

25. The product of claim 24 wherein each of said selectively sensitized photosensitive emulsion layers has predominant spectral sensitivity to separate regions of the spectrum and the dye associated with each of said emulsion layers possesses a spectral absorption range substantially complementary to the predominant sensitivity range of its associated emulsion layer.

26. The product of claim 25 wherein said photosensitive silver halide emulsion layers comprise, in sequence, a red-sensitive silver halide emulsion layer, a green-sensitive silver halide emulsion layer and a blue-sensitive silver halide emulsion layer, having associated therewith, respectively, cyan, magenta and yellow dyes, each of said dyes being silver halide developing agents.

27. The product of claim 22 which includes a diffusion transfer image-receiving element affixed at least one edge of said photosensitive element.

28. The product of claim 27 which includes a rupturable container retaining an aqueous alkaline-processing composition affixed one edge of one of said photosensitive and said image-receiving elements and adapted upon rupture to distribute its contents intermediate said photosensitive element 

2. The process of claim 1 wherein said antifoggant precursor is represented by the formula:
 3. The process of claim 1 wherein said antifoggant precursor is represented by the formula:
 4. The process of claim 1 wherein said antifoggant precursor is represented by the formula:
 5. The process of claim 2 wherein said antifoggant precursor is represented by the formula: wherein X is a divalent metal selected from the group consisting of copper, zinc, mercury, lead, tin, nickel, cadmium, cobalt, manganese, calcium and iron; Y is carbon or nitrogen; and Z is selected from the group consisting of nitrogen or C-R where R is selected from the group consisting of hydrogen or lower alkyl.
 6. The process of claim 5 wherein said antifoggant precursor is represented by the formula: where X is a divalent metal selected from the group consisting of copper, zinc, mercury, lead, tin, nickel, cadmium, cobalt, manganese, calcium or iron; and R is selected from the group consisting of hydrogen and lower alkyl.
 7. The process of claim 6 wherein said compound is zinc bis-(5-methyl-6-bromo-4-azabenzimidazolate).
 8. The process of claim 5 which includes the steps of developing said exposed photosensitive element with an aqueous alkaline processing composition forming thereby an imagewise distribution of image-forming components in said photosensitive element as a function of the point-to-point degree of exposure thereof and transferring at least part of said imagewise distribution by diffusion to a contiguous image-receiving layer to provide thereto a photographic diffusion transfer image.
 9. The process of claim 8 wherein said image-forming components comprise a soluble silver complex.
 10. The process of claim 8 wherein said image-forming components comprise color image-forming materials.
 11. The process of claim 10 wherein said color image-forming components comprise at least one dyE which is a silver halide developing agent.
 12. The process of claim 11 which includes, in combination, the steps of exposing a photosensitive element which comprises at least two selectively sensitized silver halide emulsion layers each having a dye of predetermined color associated therewith, which dye is a silver halide developing agent and is processing composition soluble and diffusible in alkali, contacting said exposed photosensitive element with an aqueous alkaline-processing composition and effecting thereby hydrolytic removal of said antifoggant moieties from said divalent metal as a function of processing temperature and development of the latent images contained in each of said silver halide emulsions, immobilizing the dye associated with each of said emulsions as a result of said development and forming thereby an imagewise distribution of mobile dye as a function of the point-to-point degree of exposure thereof, and transferring, by imbibition, at least a portion of each of said imagewise distributions of mobile dye to a superposed image-receiving element to provide thereto a multicolor dye transfer image.
 13. The process of claim 12 which includes, in combination, the steps of exposing a photosensitive element comprising blue-sensitive, green-sensitive and red-sensitive silver halide emulsion layers mounted on a common support, each of said blue-sensitive, green-sensitive and red-sensitive silver halide emulsion layers having associated therewith, respectively, yellow, magenta and cyan dyes, each of said dyes being a silver halide developing agent soluble and diffusible in alkali; contacting said exposed photosensitive element with an aqueous alkaline processing composition effecting thereby hydrolytic removal of said antifoggant moieties from said divalent metal as a function of processing temperature and development of the latent image contained in each silver halide emulsion; immobilizing said yellow, magenta and cyan dye as a function of development of their respective associated silver halide emulsions forming thereby imagewise distributions of mobile yellow, magenta and cyan dye; and transferring, by imbibition, at least a portion of each of said imagewise distributions of mobile yellow, magenta and cyan dye to a superposed image-receiving element to provide thereto a multicolor dye transfer image.
 14. The process of claim 13 wherein said antifoggant precursor is zinc bis-(5-methyl-6-bromo-4-azabenzi-midazolate).
 15. As a product, a photosensitive element which comprises a support layer carrying a photosensitive silver halide emulsion having associated therewith a hydrolyzable antifoggant precursor represented by the formula: A-X-A where each A is an antifoggant nucleus selected from the group consisting of
 16. The product of claim 15 wherein said antifoggant precursor is represented by the formula:
 17. The product of claim 15 wherein said antifoggant precursor is represeNted by the formula:
 18. The product of claim 15 wherein said antifoggant precursor is represented by the formula:
 19. The product of claim 15 wherein said antifoggant precursor is represented by the formula: wherein X is a divalent metal selected from the group consisting of copper, zinc, mercury, lead, tin, nickel, cadmium, cobalt, manganese, calcium and iron; Y is carbon or nitrogen; and Z is selected from the group consisting of nitrogen or C-R where R is selected from the group consisting of hydrogen or lower alkyl.
 20. The product of claim 19 wherein said antifoggant precursor is represented by the formula: wherein X is a divalent metal selected from the group consisting of copper, zinc, mercury, lead, tin, nickel, cadmium, cobalt, manganese, calcium and iron; and R is selected from the group consisting of hydrogen and lower alkyl.
 21. The product of claim 20 wherein said antifoggant precursor is zinc bis-(5-methyl-6-bromo-4-azabenzimidazolate).
 22. The product of claim 15 wherein said silver halide emulsion has associated therewith a dye which is a silver halide developing agent.
 23. The product of claim 22 wherein said dye is dispersed in a separate layer intermediate said silver halide emulsion and said support.
 24. The product of claim 15 wherein said support carries on one surface at least two selectively sensitized silver halide emulsion layers, each having associated therewith a dye which is a silver halide developing agent of a predetermined color.
 25. The product of claim 24 wherein each of said selectively sensitized photosensitive emulsion layers has predominant spectral sensitivity to separate regions of the spectrum and the dye associated with each of said emulsion layers possesses a spectral absorption range substantially complementary to the predominant sensitivity range of its associated emulsion layer.
 26. The product of claim 25 wherein said photosensitive silver halide emulsion layers comprise, in sequence, a red-sensitive silver halide emulsion layer, a green-sensitive silver halide emulsion layer and a blue-sensitive silver halide emulsion layer, having associated therewith, respectively, cyan, magenta and yellow dyes, each of said dyes being silver halide developing agents.
 27. The product of claim 22 which includes a diffusion transfer image-receiving element affixed at least one edge of said photosensitive element.
 28. The product of claim 27 which includes a rupturable container retaining an aqueous alkaline-processing composition affixed one edge of one of said photosensitive and said image-receiving elements and adapted upon rupture to distribute its contents intermediate said photosensitive element and said image-receiving element upon superpositioning of said elements.
 29. The product of claim 24 wherein said antifoggant precursor is dispersed in an emulsion layer of the photosensitive element.
 30. The product of claim 27 wherein said antifoggant precursor is dispersed in said image-receiving element.
 31. The product of claim 30 wherein said antifoggant precursor is zinc bis-(5-meThyl-6-bromo-4-azabenzimidazolate). 